1. Field of the Invention
The present invention relates to a backlight module and, more particularly, to a backlight module that is adaptable to a dual display module and capable of blurring the shadow image produced by the sub display window in the main display window, while the main display window is displaying images.
2. Description of Related Art
In recent years, the number of the applications using a dual display module has gradually increased, such as a clamshell cellular phone, or a wall-passing type dual display device. In the past, due to the limitation of the technology level, the dual display module could only be manufactured by connecting two display modules back to back, for displaying different images at the same time. However, this kind of dual display module not only has a certain thickness, but also has duplicated elements, such as the two backlight modules respectively for the two display modules.
For solving these two problems, a conventional backlight module applied in a dual display module is proposed, which can reduce the thickness of the dual display module and minimize the weight thereof. The structure of the conventional backlight module applied in a dual display module is shown in FIG. 1A, and FIG. 1B, wherein FIG. 1A is a perspective view of the conventional backlight module applied in a dual display module, and FIG. 1B is a cross sectional view taken along plane AA′ of FIG. 1A.
As shown in FIG. 1A and FIG. 1B, the conventional backlight module applied in a dual display module (not shown in the figures) comprises: a light guide plate 11, a light emitting unit 12, a first frame 13, a second frame 14, and a tape layer 15; wherein the light emitting unit 12 is a light emitting diode light bar located on one side edge 111 of the light guide plate 11. Besides, the first frame 13 is located below the light guide plate 11 and a first display window 131 is enclosed by the first frame 13. The second frame 14 is located above the light guide plate 11 and a second display window 141 is enclosed by the second frame 14. On the other hand, the first frame 13 has a first frame surface 132, and the tape layer 15 is located on the first frame surface 132. Upon the requirement on the optical performance of the conventional backlight module, the tape layer 15 may consist of a white tape or a black tape.
Moreover, as shown in FIG. 1A, the conventional backlight module applied in a dual display module can further comprise a first diffusing film 161 located between the tape layer 15 and the light guide plate 11, and a first brightness enhancement film 171 located between the tape layer 15 and the first diffusing film 161, wherein the first brightness enhancement film 171 is located under a whole surface of the first diffusing film 161. In the same manner, the conventional backlight module applied in a dual display module can further comprise a second diffusing film 162 located between the second frame 14 and the light guide plate 11, and a second brightness enhancement film 172 located between the second frame 14 and the second diffusing film 162.
Therefore, when the main display window (i.e. the second display window 141) of the conventional backlight module applied in a dual display module displays images, the light originally irradiated on the periphery portions of the sub display window (i.e. the first display window 131), i.e. the first frame surface 132, will arrive at the tape layer 15, instead. Therefore, only a small portion of the light will be reflected by the tape layer 15 and reach the light guide plate 11. Moreover, the tape layer 15 can only diffuse the reflected light to a limited level.
As described above, the tape layer 15 of the conventional backlight module applied in a dual display module may consist of a black tape or a white tape, but these two kinds of tapes both have their own drawbacks, which will be described later. If the tape layer 15 consists of a black tape, the shadow image produced by the sub display window in the main display window while the main display window is displaying images, will be blurred a little bit. However, since the amount of the light reflected by the tape layer 15 consists of a black tape is also reduced, the display brightness of the main display window is reduced dramatically as well. On the other hand, if the tape layer 15 consists of a white tape, the display brightness of the main display window will be maintained at a certain level. However, the shadow image produced by the sub display window in the main display window, while the main display window is displaying images, will be more obvious than the previous case.
In other words, by having the tape layer consist of a black tape or a white tape, the conventional backlight module applied in a dual display module cannot blur the shadow image produced by the sub display window in the main display window, while the main display window is displaying images, and increase the display brightness of the main display window at the same time.
Therefore, a backlight module that can blur the shadow image produced by the sub display window in the main display window, while the main display window is displaying images, and can increase the display brightness of the main display window at the same time is required.